The present invention relates to a scanning electron microscope apparatus and an evaluation system technology of a pattern, and more specifically, to a reticle inspection technology suited to perform relative position evaluation of patterns on two reticles that are used in order to form patterns on the same layer using the double patterning technology.
For critical dimension evaluation of a reticle pattern, the transmission-type optical microscopes have been used, partly because the reticle is used in a usage of transferring a light transmittance pattern. However, it has become difficult to measure the pattern optically as the pattern becomes finer, and it becomes indispensable to use a scanning electron microscope (SEM) having a higher resolution for patterns (pattern elements) of smaller than 90 nm.
In recent years, in order to attain more minute patterns further, super micro-machining technologies called RET (Resolution Enhancement Techniques), for example, OPC (optical proximity correction) and DPT (double-exposure, double-patterning), are used, and consequently it has become necessary to evaluate accuracy of a pattern using the electron microscope. It is known that a pattern manufactured using these technologies easily becomes a resolving difficult spot (hot spot) that produces a cause of defective transfer, such as a short (a short circuit) and a disconnection. Especially, in the double-patterning, since the patterning is conducted on the same layer by two times of processing in contrast to the conventional pattering, the relative position between the two reticles has become important. However, a current situation is that CD measurement of the reticle pattern using the electron microscope is mainly performed on critical dimensions (CD's) of a single pattern and between plural patterns, and it cannot be said that a technique of evaluating the relative position between the two reticle patterns has been established.
As a method for measuring the relative position between the patterns existing on plural layers, a method for evaluating overlaying accuracy using reticle pattern images acquired by the electron microscope (for example, see JP-A-2007-121607) and a method for measuring patterns on a wafer by irradiation of a high-voltage electron beam (for example, see JP-A-11-44664) have been developed.
JP-A-2007-121607 describes a technique whereby an image is acquired for a reticle having a defective inclusion pattern by the electron microscope, an image of a substrate is obtained by performing a lithography simulation on this, an inclusion distance is calculated by overlaying the two pattern images at the same coordinates, and it is judged whether it satisfies the defined value. The use of this technology makes it possible to estimate, at the time of reticle formation, the relative position between the patterns existing on plural layers that cannot be inspected with a low-voltage electron microscope after pattern completion.
JP-A-11-44664 describes a technology of directly measuring the relative position between the patterns existing on plural layers using an electron microscope with an acceleration voltage of 100 to 500 kV.